Bullets used for law enforcement and self-defense are normally designed to provide a desired performance in terms of penetration and expansion. Expansion generates a larger wound channel, thereby more rapidly disabling a threat. Penetration is desirable to a degree to provide a deeper wound channel. Under penetration or excessive penetration is not desired because of the risk of lack of incapacitation or risk to innocents behind the target threat, and because of the energy wasted in a bullet that continues beyond the threat.
Law enforcement personnel are particularly concerned with the effectiveness of bullets on a threat that is behind a barrier. Typical bullet performance tests include positioning a block of ballistic gelatin behind a barrier, and then measuring the penetration of the gelatin by a bullet that passes through the barrier. Barriers may include two layers of gypsum wallboard (simulating a residential wall), 2 layers of sheet metal (simulating a car door), a sheet of ¾″ plywood, and a sheet of auto glass. These tests represent the reality that law enforcement officers may need to stop a criminal threat which is barricaded behind such barriers (unlike self-defense situations, where a barricaded threat can more realistically be fled).
Ideally, the bullet penetrates a block of gelatin by at least 12″ after passing through the barrier. This is a challenge for conventional hollow-point rounds designed to expand on first contact (typically, with flesh) because these soft and fragile bullets that expand readily are more likely to fragment or otherwise be distorted by the barrier, leaving a less-lethal resulting portion that may penetrate insufficiently.
Typical hollow point design bullets also tend to perform inconsistently. The damage suffered by the bullet upon striking the barrier is widely inconsistent, which means subsequent gel penetration is also inconsistent (often being inadequate) to be considered effective. There is also inconsistency for typical bullets as they perform on different barriers. One design might be effective after passing through drywall or plywood, but ineffective after penetrating auto glass (which is considered to be one of the most challenging elements of bullet performance tests). Bullets that perform well on bare or clothed gel alone (soft and easily-expanding bullets) often perform poorly on hard barrier tests. Bullets that perform well on barriers (solid bullets and bullets made from hard alloys of lead) tend to over penetrate dangerously on bare or clothed gelatin (where penetration in excess of 18-24″ is considered dangerous).
As shown in U.S. Pat. No. 8,161,885 to Emary, the disclosure of which is incorporated by reference herein, hollow point bullets are found to perform more effectively when the cavity is filled with an elastomeric nose element. The elastomeric nose element allows the use of harder lead alloy bullets than are normally considered suitable for expanding pistol bullets, which normally use soft pure lead. The elastomer-filled cavity bullets allow the use of harder alloys because the elastomeric nose insert provides a force to expand the bullet. Along with being unusually effective, the hard lead alloy bullets also increase consistency and post-barrier performance in these bullets.
As background, it is noted that certain bullets are provided with a “cannelure,” which is a circumferential groove typically made to a limited depth in the jacket, which happens to deflect the jacket slightly inward when formed. Cannelures are used in rifle bullets (which are seated in a chamber based on the position of the shoulder of a bottlenecked cartridge) to enable the case mouth edges to be deformed inward into the cannelure to securely grip the bullet. This is important during recoil when prior rounds are fired. Cannelures are also used for higher-powered, rimmed revolver bullets, such as 357 and 44 Magnum calibers, which are axially located in the cylinder of a revolver by the rims. These cartridges generate substantial recoil, and the cannelure secures the bullet.
Cannelures are not used for bullets used with auto-loading pistol cartridges such as .45 ACP, .40 S&W, and 9 mm Luger. The recoil forces are not significant enough to make the cannelure necessary, and more importantly, such cartridges headspace at the case mouth. This means the case mouth provides a ledge that stops against a ledge in the pistol chamber when the round is fully chambered. Cannelures have not been used in automatic pistol cartridges because great care must be taken to make sure the case mouth is not excessively bent inward into the cannelure as in other cannelured cartridges, and thus fail to present an edge to engage the ledge in the chamber. In the absence of a sufficient ledge on the case mouth, the cartridge would insert excessively. Either primer strikes might not be effective (resulting in a failure to fire), or excess space between the base of the case and the face of the bolt would cause the case to be unsupported, and thus prone to case separations, with the attendant risk to the shooter and potential inability to fire critical follow-up shots.
Moreover, forming cannelures in bullets when not required makes the cartridge manufacturing process more challenging because of the need to more precisely set the insertion depth of each bullet to put the cannelure at the right location with respect to the case mouth.
Therefore, a need exists for a new and improved pistol bullet that penetrates a variety of barriers, but does not over penetrate bare or clothed gelatin. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the ballistic barrier according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of penetrating a variety of barriers without over penetrating bare or clothed gelatin.